I had 4 (2m/2f) until a few days ago, then one of the males suddenly looked bloated and died the next day. It happened literally overnight, I was turning off the lights and found him near the surface with most of his color faded away. Belly was quite swollen, and he was dead the next morning. I was curious about what caused it, thought maybe it was something he ate, so I sliced his belly open with a razor blade. A little pressure squeezed out several globs of transparent jello-like material that was apparently what had caused the swelling. None of the other fish (eureka red group, ruby green Hap, Synodontis multi's, 3-4 different species of silver dollars, BN pleco's, and a single black tetra) appear to have any problems, but that male looked fine the day before.
How big is your female? My group are all about 4-5" now, the 2 females a little smaller than the remaining male.